The present application claims priorities under 35 U.S.C. xc2xa7119 to Japanese Patent Applications No. 2000-245038, filed Aug. 11, 2000 and Japanese Patent Application No. 2000-337810, filed Nov. 6, 2000, entitled xe2x80x9cMANUFACTURING METHOD OF CUSHION MEMBERxe2x80x9d. The contents of this application are incorporated herein by reference in their entirety.
1. Field of the Invention
The present invention relates to a manufacturing method of a cushion member which is used in a seat such as a sofa or the like within a vehicle, an airplane a ship or a room.
2. Description of the Background
Conventionally, a seat portion in a seat of a motor vehicle or the like is constructed such that a cushion member used in an inner portion thereof has a two-layer structure including a soft layer and a hard layer, so that the comfort of a user sitting on the seat is improved thereby.
As a method of manufacturing the cushion member having the two-layer structure mentioned above, for example, there is a method disclosed in Japanese Examined Patent Publication No. 6-11496 (a prior art 1). In accordance with this method, in a molding die for forming the cushion member, there is provided a side partition between a center cavity for forming a first center portion in the seat portion of the seat and a side cavity for forming side portions positioned in both right and left sides. Further, in the center cavity, there is provided a front and rear partition for partitioning between a front portion and a rear portion.
Then, a soft raw material is injected to the front portion mentioned above, thereafter a hard raw material is injected to the other portions, whereby a soft layer is formed below the front portion, that is, in an obverse side in a front portion of the seat portion, and a hard layer is formed above the front portion, that is, in a reverse side in the front portion of the seat portion and side portions and the rear portion of the seat portion, so that the cushion member having the two-layer structure is formed.
However, the conventional manufacturing method of the cushion member mentioned above has the following problem.
That is, in the manufacturing method in accordance with the prior art 1, a flow amount of the hard raw material later injected is not restricted at all at a time of molding by injecting the soft raw material and the hard raw material to the molding die. Accordingly, it is hard to keep a thickness of the soft layer and the hard layer to a predetermined thickness, so that a dispersion is necessarily generated locally or between production lots.
As the other conventional embodiments, for example, there are structures described in Japanese Unexamined Patent Publication No. 10-225943 (a prior art 2) and Japanese Unexamined Patent Publication No. 2-140107 (a prior art 3).
In the prior art 2 mentioned above, an injection hole for injecting a molding material and a closing lid mounted via a hinge portion for closing the injection hole after injecting the molding material are provided in a boundary member. At a time of forming the cushion member, the boundary member is arranged in a molding die for the cushion member, one molding material is injected from the injection hole, and another molding material is injected to an upper portion of the boundary member. Then, one molding material injected from the injection hole rotates the hinge portion by a foaming force thereof, whereby the closing lid closes the injection hole. Accordingly, the cushion member having the two-layer structure gripping the boundary member therebetween is formed.
In the prior art 3 mentioned above, a molding die for the cushion member has a middle frame between an upper die and a lower die, and the boundary member is arranged in the middle frame. Then, one molding material is injected to the lower die. Thereafter the middle frame is closed, next another molding material is injected in an upper portion of the middle frame, thereafter the upper die is closed and a foaming process is executed. Accordingly, the cushion member having the two-layer structure gripping the boundary member therebetween is formed.
However, in the conventional manufacturing method of the cushion member mentioned above, there is the following problem.
That is, in the prior art 2 mentioned above, as mentioned above, it is necessary that the closing lid having the injection hole and the hinge portion are provided in the boundary member, and in the prior art 3, it is necessary that the middle frame is provided in the molding die in the manner mentioned above. In other words, in the prior arts mentioned above, the special structure is required in the boundary member or the molding die at a time of injecting.
In order to improve the above problems, in the prior art 2 mentioned above, there is another forming method in which a flexible partition member is used in the boundary member mentioned above and an injection port for the molding material is provided in the flexible partition member. However, in this forming method, it is impossible to enlarge the injection port enough and it is not easy to inject the molding material.
According to one aspect of the present invention, there is provided a manufacturing method of a cushion member for executing an expansion molding by using an upper die and a lower die, in which in the lower die, a first cavity for forming a first center portion having an obverse layer portion positioned in an obverse side of the cushion member and a reverse layer portion positioned in a reverse side of the cushion member, and a second cavity for forming a second center portion arranged at the rear of the first center portion are formed, and a front and rear partition is provided between the first cavity and the second cavity. The upper die has a bottom portion forming surface for forming a bottom portion of the cushion member. At a time of executing the expansion molding, a first raw material having a foaming property is injected to the first cavity and a second raw material having a foaming property and forming a foamed product having a different physical property from that of a foamed product formed of the first raw material at a time when the foaming process is completed is injected to the second cavity. Thereafter, the lower die and the upper die are closed so as to form a flow port between the bottom portion forming surface in the upper die and an upper end of the front and rear partition, the second raw material flows within the first cavity while being limited in a flow amount by the flow port and flows forward so as to follow the flow of a flow front end portion of the first raw material while covering over the first raw material so as to restrict an upward foam flow of the first raw material. Finally, the first raw material forms an obverse layer portion below the first cavity, and forms a front edge portion in a forward end portion of the first cavity, and on the other hand, the second raw material forms the reverse layer portion above the first cavity, and forms the second center portion in the second cavity.
A remarkable aspect of the present invention is that the lower die and the upper die are closed so as to form a flow port between the bottom portion forming surface and an upper end of the front and rear partition in the upper die, and the second raw material flows within the first cavity while being limited in a flow amount by the flow port and flows forward so as to follow the flow of a flow front end portion of the first raw material while covering over the first raw material so as to restrict an upward foam flow of the first raw material.
Next, a description will be given of an operation and effect of the present invention.
In the present invention, the first raw material is injected in the first cavity so as to foam and flow within the first cavity. Further, the second raw material is injected in the second cavity so as to ride over the front and rear partition and also foam and flow in the first cavity.
Then, the lower die and the upper die are closed after the injection of the second raw material is completed. At this time, the flow port is formed between the bottom portion forming surface of the upper die and the upper end of the front and rear partition.
Accordingly, it is possible to restrict the flowing direction and the flow amount of the second raw material flowing so as to follow to the flow front end portion of the first raw material. Further, the second raw material foams and flows forward so as to cover over the first raw material, and flows forward while preventing the first raw material from foaming and flowing upward without limitation, due to its weight. Accordingly, it is possible to foam and flow the first and second raw materials with a fixed speed. Therefore, the obverse layer portion made of the first raw material and the reverse layer portion made of the second raw material can be formed without dispersion in their thickness.
Since the flow of the first raw material toward the front portion of the flow front end portion is promoted by the second raw material, the flow front end portion is prevented from further forward flowing when it reaches the forward end portion of the first cavity. On the other hand, the flow front end portion is prevented from backward flowing by the flow of the chasing second raw material and flows toward the upper portion of the front edge portion.
Accordingly, the first raw material can surround an outer side of the second raw material so as to form the front edge portion in the forward end portion of the first cavity.
Accordingly, it is possible to form the cushion member having the two-layer structure including the reverse layer portion and the obverse layer portion, in which almost all the surface of the first center portion and the surface of the front edge portion in the cushion member are formed by the foamed product of the first raw material.
As mentioned above, in accordance with the present invention, it is possible to provide a manufacturing method of the cushion member which has a two-layer structure including an obverse layer portion and a reverse layer portion, and has no dispersion of thickness between the obverse layer portion and the reverse layer portion.
According to another aspect of the present invention, there is provided a manufacturing method of a cushion member for executing an expansion molding by using an upper die and a lower die, in which at a time of executing the expansion molding, a flexible film is arranged in a cavity in the lower die so that an opening portion to which a first raw material having a foaming property flows is formed between an end portion of the flexible film and the cavity. The first raw material flows from the opening portion, and a second raw material having a foaming property and forming a foamed product having a different physical property from that of a foamed product formed of the first raw material at a time when the foaming process is completed is injected from the portion other than the opening portion, and
thereafter, the lower die and the upper die are closed so as to integrally expansion mold the first raw material and the second raw material by setting the flexible film to be a boundary layer, thereby forming the cushion member having the two-layer structure including a first foamed product made of the first raw material and a second foamed product made of the second raw material and interposing the flexible film between the two.
A remarkable aspect of the present invention is that the flexible film is arranged in the cavity in the lower die so that the opening portion is formed, the first raw material is flowed from the opening portion, and the second raw material is injected from another portion than the opening portion, thereby forming the cushion member having the two-layer structure gripping the flexible film therebetween.
Next, a description will be given of an operation and effect of the present invention.
In the present invention, the flexible film is arranged at an optional position of the cavity in the lower die while holding the opening portion. The opening portion is formed so as to section a part of the cavity while the cavity is continuously connected.
Next, the first raw material is flowed from the opening portion, and on the other hand, the second raw material is injected from the portion other than the opening portion. Then, the first raw material and the second raw material respectively flow in the lower portion of the flexible film and the upper portion of the flexible film while foaming in a state of being moved apart from each other by the flexible film.
That is, in the cavity in the lower die, at the portion where the flexible film is arranged, the first raw material and the second raw material independently foam and flow while giving no influence to each other. Accordingly, at the portion where the flexible film is arranged, it is possible to prevent the first raw material and the second raw material from being mixed with each other, and it is possible to form the cushion member in which the thickness of the first and second foamed products is stable.
The flexible film has flexibility and can be arranged at an optional position in the cavity of the lower die. That is, in the case that it is intended to change the shape of the two-layer structure of the cushion member, the flexible film can be easily modified by changing the arranging state of the flexible film. Accordingly, it is possible to easily form the cushion member having an optional shape of the two-layer structure.
The flexible film has the opening portion and is structured such that two layers are not completely separated by a boundary member in the same manner as the conventional one. Accordingly, it is not necessary to restrict the order of injection of the molding material such that the second raw material is injected after finishing the injection of the first raw material at a time of forming, and it is also unnecessary to previously form the injection hole in the boundary member in order to avoid the matter. Therefore, it is easy to inject the forming material of the first raw material and the second raw material, it is possible to inject at an optional timing and it is possible to easily form the cushion member.
In the formed cushion member the flexible film is gripped between the first foamed product and the second foamed product. The flexible film is excellent in elastic deformation and hardly influences properties such as an impact reducing property of the cushion member and the like due to a combination of the first foamed product and the second foamed product. Accordingly, it is possible to form a cushion member having excellent properties.
The cushion member is taken out while gripping the flexible film after being formed. Accordingly, it is easy to take out the cushion member.
It is preferable to use a material having an improved adhesive property with respect to the first foamed product and the second foamed product, for the flexible film. In this case, it is possible to improve a general degree of bond in the cushion member after being formed.
As mentioned above, in accordance with the present invention, it is possible to provide a manufacturing method of the cushion member which can easily form the cushion member having an optional shape of a two-layer structure and having excellent properties, and inject the molding material easily and at an optional timing.